The prized Koi fish, more properly known as Nishikigoi, are the result of a few hundred years of selective breeding between the Asian carp and German carp. Colour permutations began to appear on this long-lived fish around 1800. It's not unheard of for a properly cared for Koi fish to live 30 years. The Japanese record is an astounding 223 years. If the climate is not too cold, Koi do quite well in either outdoor ponds or aquariums but, today, the focus is on an aquarium set-up.
One of the first habits a Koi owner should develop is to watch for signs of stress and disease in the fish. Behaviours like clamped fins, odd swimming patterns, red or white sores, gasping at the surface, crashed on the bottom, or a loss of appetite are all signs that something is amiss in the aquarium. The critical idea is to catch any problems early. Chances for a full recovery increase the sooner you notice there is trouble.
Temperature and Water
While Koi fish can survive well in an unheated aquarium, they won't do well if there are rapid temperature fluctuations. If the temperature regularly falls to 10 degrees Celsius or below, the chance of becoming ill increases with the more exotic breeds. Common Koi should still do well in that environment.
Refrain from putting your Koi fish in a simple water bowl style aquarium. They need aerated, clean water. Though Koi are easy to maintain, a bowl setting can lead to nitrate poisoning, as well as stunted growth. In a healthy environment Koi fish can grow up to three feet in length.
You will need the following list of items to get your Koi aquarium up and running: aquarium, air pump, filtering equipment, water thermometer, fluorescent light, glass lids for aquarium, gravel, heater, thermostat, dechlorinator, fish net and food.
After choosing a suitable spot for the aquarium, put the gravel in the bottom. Next, connect the filter, pump, thermostat and other system parts. Add decoration, water, dechlorinator, and turn everything on. Add the Koi fish and you're done. Feed your Koi twice daily, never putting more in the tank than can be eaten within a few minutes, and never put too many in the aquarium. They need room to swim and grow. Every two or three weeks you should change one-third of the water and remove detritus from the floor.